fix: help message flags, removes -f flag and adds -g flag (#5685)

Closes #5682

- Removes the broken `-f` flag from the help message which doesn't
behave as expected as an alternative to `--features`.
- Adds the `-g` flag to the help message which is a working alternative
to the `--githash` flag.

src/util/shell.cpp

@@ -192,9 +192,9 @@ static void display_help(std::ostream & out) {
     display_header(out);
     std::cout << "Miscellaneous:\n";
     std::cout << "  -h, --help             display this message\n";
-    std::cout << "  -f, --features         display features compiler provides (eg. LLVM support)\n";
+    std::cout << "      --features         display features compiler provides (eg. LLVM support)\n";
     std::cout << "  -v, --version          display version number\n";
-    std::cout << "      --githash          display the git commit hash number used to build this binary\n";
+    std::cout << "  -g, --githash          display the git commit hash number used to build this binary\n";
     std::cout << "      --run              call the 'main' definition in a file with the remaining arguments\n";
     std::cout << "  -o, --o=oname          create olean file\n";
     std::cout << "  -i, --i=iname          create ilean file\n";